ENH: Implement DataFrame.astype('category') by jschendel · Pull Request #18099 · pandas-dev/pandas (original) (raw)

Updated to address the comments:

• Modified the DataFrame constructor to be consistent with DataFrame.astype
  • Modified categorical.rst to reflect this
  • Added this to the breaking API changes section of the whatsnew
• Moved logic to the _get_categorical_dtype_2d helper function in categorical.py
• Created unique2d and _ensure_arraylike2d functions in algorithms.py
• Added tests for the three items above

Regarding _ensure_arraylike2d, the reason I created this was because I was running into an issue with _ensure_arraylike where a list of lists gets returned as a numpy array of lists instead of a 2d numpy array:

In [22]: values = [['a', 'b', 'c', 'a'], ['b', np.nan, 'd', 'd']]

In [23]: _ensure_arraylike(values) Out[23]: array([list(['a', 'b', 'c', 'a']), list(['b', nan, 'd', 'd'])], dtype=object)

whereas I'd like to get output along the lines of:

In [24]: np.array([_ensure_arraylike(x) for x in values]) Out[24]: array([['a', 'b', 'c', 'a'], ['b', nan, 'd', 'd']], dtype=object)

Should I just try patching _ensure_arraylike instead of creating _ensure_arraylike2d? Or is what I did fine?